In general, where an ordinary general-purpose engine is employed in a working machine or the like, the engine is deactivated or stopped by a human operator operating a main switch to a stop position to turn off an ignition device. Negative pressure in the interior of a Venturi section of a carburetor is canceled by the deactivation of the engine. As a consequence, fuel spray from a fuel chamber, provided in the carburetor, into the Venturi section is stopped.
However, due to inertia, the engine completely stops after having continued rotation for a certain time. Namely, some idling time is required before the engine completely stops. If an air-fuel mixture is supplied from the Venturi section of the carburetor to the engine during the idling, there can occur a so-called afterburn in which the air-fuel mixture remains unburned in the engine and muffler and temporarily ignites. A technique for preventing such an afterburn is known, for example, from Japanese Patent Application Laid-open Publication No. 2005-133564 (hereinafter “the relevant patent literature”).
A fuel supply apparatus for an engine (engine fuel supply apparatus) disclosed in the relevant patent literature includes an electromagnetic valve (fuel shutoff valve) in a fuel supply line for supplying fuel from a fuel tank to a fuel chamber of a carburetor. A control section performs control for automatically closing the electromagnetic valve for a predetermined time after the engine is deactivated by an operation of a main switch. As a consequence, the fuel supply from the fuel tank to the fuel chamber is shut off until the engine is completely deactivated.
However, the fuel supply apparatus disclosed in the relevant patent literature employs a multiplicity of electric component parts, such as the electromagnetic valve, the control section for controlling the electromagnetic valve, and a power supply section for supplying electric power to the electromagnetic valve and the control section. As known, general-purpose engines are less costly than vehicle engines. Thus, employing the multiplicity of electric component parts in such an inexpensive general-purpose engine would lead a great ratio of the total cost of the electric component parts to the overall cost of the entire general-purpose engine. Because employing the multiplicity of electric component parts becomes a cause for a cost increase of the general-purpose engine, the fuel supply apparatus disclosed in the relevant patent literature is yet to be improved.